The present invention relates to storage library subsystems as commonly used in the computer data storage arts. Specifically, the present invention relates to the management of storage cartridges by the robotic retrieval and delivery of the cartridges from one location to another within a storage library subsystem. More specifically, the present invention relates to a robotic shuttle""s gripping fingers and the associated method by which those fingers grip and release storage cartridges within a storage library subsystem.
Storage library subsystems provide large capacity secondary storage to modem computing environments. Such storage library subsystems typically employ robotic control mechanisms to physically manage storage cartridges used by host computer""s system.
A plurality of storage cartridges are stored within the storage library subsystem either in a linear, a rectangular or a cylindrical array. Each storage cartridge is in a particular slot in the library subsystem. Each slot is identifiable by its physical position within the library subsystem.
The subsystem maintains inventory information to associate a particular cartridge with a particular slot in the subsystem.
Responsive to a host computer system request, an appropriate storage cartridge is physically retrieved from its associated slot in the library, moved to an appropriate read/write device for processing, and inserted into that device. Conversely, when the use of the storage cartridge is complete, the cartridge is retrieved by the robotic mechanism from the read/write device, moved adjacent its associated slot according to the inventory maintained by the subsystem, and inserted into the storage slot of the library ready for future use in response to another host computer system request.
Over time, computing environments have tended to become smaller and less centralized. Prior storage library subsystems were often costly, complex and bulky. While arguably appropriate for centralized large data processing environments, prior storage library subsystems were inappropriate in the more modem decentralized workgroup environments. In these environments, reduced costs, complexity and size of storage library subsystems are essential features.
Related art discloses several data storage options with associated pick and place mechanisms that offer cost, complexity and size reductions. These pick and place mechanisms are notable for their design of a gripping means that is convertible between a retrieval mode, in which the gripping means is capable of engaging and carrying a storage cartridge, and a return mode, in which the gripping means releases the storage cartridge so that the cartridge may be returned to a drive or its storage position.
One presently available cartridge retrieval mechanism, described in U.S. Pat. No. 5,450,391, utilizes a carriage that is slidable along a longitudinal base with attached gripping arms that are pivotally mounted on the carriage. These gripping arms are configured such that when they are advanced against a storage cartridge, they will deflect laterally around the corners of the cartridge until they engage the recessed notches of the cartridge. The ""391 patent teaches that two setting components control whether the gripping arms are in the engaged position or the relaxed position. These setting controls are likewise controlled by camming members that exist along the extension and retraction path of the slidable carriage and that trigger the setting components by their physical interaction with the carriage.
Similarly, U.S. Pat. No. 5,691,859 also utilizes a slidable carriage with pivotally mounted gripper arms useful for picking and placing storage cartridges within a library subsystem. The ""859 patent is similar in that two camming members and a gripper-tripping projection located on the magnetic drive""s bezel independent of the slidable carriage dictate the positioning of the gripper arms. Unlike the ""391 patent, the ""859 patent teaches a method of cartridge picking that allows the arms to avoid contact with the storage cartridge until the moment of actual engagement in which the gripper arms lock into the recessed notches of the cartridge.
In both patents, and in other related art disclosures, the gripper arms are naturally biased in an open position. Setting the gripper arms for both the retrieval and the return modes is accomplished by mechanical actuators that exist independent of the slidable stage/gripper arm assembly. What is needed is an inexpensive, simplified, and integrated gripper arm/transport assembly that does not require an independent triggering mechanism to set the gripper arms into position for either cartridge extraction or placement. Especially desirable would be an integrated gripper actuator mechanism that improves upon the related art in picking and placing storage cartridges from a multi-position storage magazine to a tape drive with minimal maintenance and with minimal operator interaction.
The present invention solves the above problems and thereby advances the art by providing a simpler apparatus and corresponding method to retrieve and deliver storage cartridges within a storage library subsystem. Although a tape storage cartridge system is detailed below as the preferred embodiment of the invention, one skilled in the art would recognize that this invention is useful in other storage cartridge systems. The present invention discloses a new robotic shuttle that will pick a tape storage cartridge from a multiple-position storage magazine and place it in a tape drive. In an exemplary embodiment of the present invention, the means to activate and de-activate the gripper arms assembly are located entirely within the motorized stage. The gripper arms are geometrically cammed open by the storage cartridge and fall into the storage cartridge""s notched recesses in combination with the gripper arms"" bias springs. The gripper arms are forced open in the cartridge placement phase when an integrated solenoid is activated, forcing a mechanical trigger to trip the lower gripper finger in a camming motion that releases the cartridge. The gripper arms"" engaging position is reset when the solenoid deactivates upon the withdrawal of the motorized stage from the placement phase. The simplicity of the library system and the linear drive train upon which the motorized stage travels ensures low initial cost, and ease of maintenance and of use, which addresses the needs of the end user. Previous related art feature more complex apparatus and therefore decrease overall reliability through downtime for repair or adjustment that is too costly to justify.
The tape storage cartridge picking and placing apparatus and its associated method are the essential inventions. The robotic shuttle incorporates upper and lower spring-loaded, gripping fingers that are inter-connected by way of a pivot link, attached to the lower gripping finger, and a connecting link, attached to the upper gripping finger, that are themselves inter-connected by a pin. The gripping fingers are mounted to a motorized stage (the Z-stage) that extends from and retracts into the housing of the robotic shuttle (the X-plate) along the Z-axis. The Z-stage is affixed to the X-plate which, in turn, employs a mounted threaded nut to its top panel, that is bi-directionally driven on a worm screw along the X-axis by a motor enabling the robotic shuttle to move cartridges from storage locations to the tape drive and back.
In order to pick a tape storage cartridge, the Z-stage extends distally along the positive Z-axis from the X-plate toward the cartridge magazine. As the spring-loaded, gripping fingers contact the stored cartridge, the cartridge""s corners deflect the gripping fingers around the outside of the cartridge in a camming motion against the bias of the springs. The gripping fingers travel around the cartridge""s corners and over the cartridge""s edges until they reach the standard recessed notches on the top and bottom of the cartridge. Due to the complimentary geometry of both the recessed notches and the spring-loaded, gripping fingers, the gripping fingers snap into the cartridge""s recessed notches and securely grasp the cartridge for movement in the opposite direction along the negative Z-axis. When the cartridge is fully extracted from the multipleposition storage magazine and the Z-stage fully retracted into the X-plate, the picked cartridge is ready for a longitudinal move along the X-axis toward the tape drive.
To place a tape storage cartridge either in the tape drive or into the multiple-position storage magazine, a push-type solenoid is energized when the Z-stage once again begins to extend along the positive Z-axis. The solenoid is connected to a mechanical trigger, which in this preferred embodiment of the invention, is comprised of a catch-link with a catch-pin affixed to its distal end. The catch link, catch-pin combination is at rest in a down position, but rotates upward into the path of the lower gripping finger when the catch-link is activated by the solenoid. As the Z-stage approaches the storage magazine, and after the cartridge has entered the storage magazine or tape drive, the catch-pin engages the lower gripping finger applying a force that, in combination with the force of the Z-stage""s motion, forces the lower gripping finger and the connected upper gripping finger to release the cartridge""s notched recesses. Those skilled in the art will recognize that there a numerous mechanical trigger designs that are capable of the same function. As the Z-stage gets closer to the end of its Z extension, the gripping fingers open further, enabling them to clear the cartridge""s notched recesses and the cartridge""s upper and lower corners, while the leading edge of the Z-stage pushes the cartridge to its seated position within the storage magazine. At this point, the Z-stage withdraws from the storage magazine and travels back to the X-plate along the negative Z-axis, and the upper and lower spring-loaded, gripping fingers reset, awaiting another X-axis move to pick and place another cartridge.